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A n alarming new medical study has found nine different kinds of microplastics in human stool samples from around the world. The plastics include several varieties that are commonly used in food packaging and water bottles.

This finding confirms what researchers have long suspected: The plastics we use in food processing and storage are making their way into the human gastrointestinal tract.

The term “microplastics” has emerged as the consensus label for tiny particles of plastic that are less than five millimeters in diameter — about the size of a sesame seed. They're typically generated by the breakdown of larger pieces of plastic through normal wear and tear.

The field of microplastics is a very busy area of study, particularly among marine biologists and oceanographers. According to the National Oceanic and Atmospheric Administration (NOAA), microplastics are a significant threat to ocean health and marine species. The tiny particles can pass through water filtration systems and end up clustering in giant floating waste fields.

“Now that we have first evidence for microplastics inside humans, we need further research to understand what this means for human health.”

For several years now, marine scientists have been warning that these ocean plastics are getting into the food supply via fish and other ocean animals. The latest research suggests that microplastics are also entering the human body even more directly.

In the new pilot study, scientists monitored a small group of eight participants from eight countries across the world: Finland, Italy, Japan, the Netherlands, Poland, Russia, the U.K., and Austria. Their stool samples were tested for 10 types of plastics using a newly developed analytical procedure. The participants each kept a food diary as well.

Every stool sample tested positive for some microplastic. Analysis suggests that the plastics were introduced to the body via plastic-wrapped food and water bottles.

On average, the researchers found 20 microplastic particles per 10 grams of stool. In some participants, as many as nine different plastics were found, sized between 50 and 500 micrometers. The most frequently found types of plastic were polypropylene (PP) and polyethylene terephthalate (PET), which are the two most common kinds of plastic used in food packaging and labeling.

Lead researcher Philipp Schwabl of the Medical University of Vienna is presenting the findings today at UEG Week, Europe's largest meeting of gastrointestinal researchers. The study was organized by the Medical University of Vienna and the Environment Agency Austria.

“Of particular concern is what this means to [medical professionals] and patients with gastrointestinal diseases,” Schwabl said in an announcement of the new study.

Microplastics could affect the tolerance and immune response of the GI tracts by accumulating dangerous amounts of toxic chemicals and pathogens, the research team said.

Schwabl notes that the risks aren't limited to the GI tract.

“While the highest plastic concentrations in animal studies have been found in the gut, the smallest microplastic particles are capable of entering the bloodstream, lymphatic system, and may even reach the liver,” he said. “Now that we have first evidence for microplastics inside humans, we need further research to understand what this means for human health.”